CIBJO releases Gemmological Special Report: considers process of separating measurable facts from opinion; See Gemological Articles below.
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 Post subject: Sunset Quartz
PostPosted: Mon Apr 27, 2009 11:04 am 
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Sunset quartz was discovered in 2006 in Minas Gerais, Brazil.
It was in very limited supply, with the vein producing only 5 kg. of gem quality material total.
Yesterday, Karim paid me a visit and had a tremendous personal collection of Sunset Quartz that I would like to share with you.

The yellowish and orange color of the quartz is the result of microscopic acicular (needle-like) inclusions. Analysis of these inclusions, reported in Gems & Gemology in Winter 2006, determined that they were NOT rutile as we might have suspected but were composed of Si, Al and Fe with traces of K! The identification of the actual mineral was inconclusive.
The material is semi-transparent to translucent with a milky consistency.
The RI, Birefringence, SG is typical of quartz.


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PostPosted: Mon Apr 27, 2009 11:24 am 
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Hi Barbra,

Neat looking material, I'm wondering if the inclusions could be that of limonite?

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bear


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PostPosted: Mon Apr 27, 2009 11:33 am 
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Here is the pic I just snapped of the inclusions at 40X, dark field illumination:
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PostPosted: Mon Apr 27, 2009 12:11 pm 
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Wow nice stuff..it's just like rose quartz but a different color..translucent..needle-like inclusions..etc. Nice stuff. So it's pretty rare with only 5kg of stuff..glad you got a hold of some to take pics, barbra! Did you get to keep any?

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PostPosted: Mon Apr 27, 2009 12:27 pm 
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Here's a similar shot, but with a bit more light through the stones.

Image

As a sense of scale, that large rectangular stone is 4.07 carats. The largest known faceted gem example is 19.5 carats.


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PostPosted: Mon Apr 27, 2009 12:53 pm 
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Bear Williams- SGL wrote:
Hi Barbra,

Neat looking material, I'm wondering if the inclusions could be that of limonite?

___
bear

That would make sense, Bear, especially considering the story in the latest G&G about how inclusions misidentified in Brazilian topaz as rutile needles have been subsequently identified as acicular limonite.
But, I'm not personally determining that these inclusions were unidentifiable, I copied it from the 2006 G&G article.
:D


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PostPosted: Mon Apr 27, 2009 1:09 pm 
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amethystguy wrote:
Wow nice stuff..it's just like rose quartz but a different color..translucent..needle-like inclusions..etc. Nice stuff. So it's pretty rare with only 5kg of stuff..glad you got a hold of some to take pics, barbra! Did you get to keep any?

Yes, I did get to keep one....
Image
It weighs 1.68 carat and it is the host of the inclusions I pictured above.


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PostPosted: Mon Apr 27, 2009 1:24 pm 
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It seems to have a haziness to it..an "aura" if I may..very cool. glad you got one..I bet that one goes up on the ole' shelf with your other goodies

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PostPosted: Mon Apr 27, 2009 1:35 pm 
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The GIA described the diaphaneity as semi-transparent or milky... I think we'd all agree with that.
The gem has already been given a prominent new home on my orange tray, next to my East African Illusion Sunstone. :D


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PostPosted: Mon Apr 27, 2009 1:37 pm 
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Here's a shot through a 20x Belomo loupe. You can make out some of the accicular inclusions as well as another "weird" inclusion. This is the largest trillian in my photo. The plane on the weird inclusion is about 45 degrees out from the photo... the right end is closer and the left end is farther.

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PostPosted: Mon Apr 27, 2009 2:23 pm 
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Just a note to add to Barbra's description of the chemical composition of the inclusions. G&G notes that the Si content of the inclusions was LESS than in the surrounding quartz.


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PostPosted: Mon Apr 27, 2009 4:14 pm 
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Very pretty stones Barbra and Karim! Love the inclusion shot.


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PostPosted: Mon Apr 27, 2009 11:16 pm 
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Carrie wrote:
Very pretty stones Barbra and Karim! Love the inclusion shot.


I agree - gotta love the colour and the inclusions (and their overall effect).


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PostPosted: Tue Apr 28, 2009 12:28 pm 
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gem-n00b wrote:
Just a note to add to Barbra's description of the chemical composition of the inclusions. G&G notes that the Si content of the inclusions was LESS than in the surrounding quartz.


Perhaps this belongs in the Gem Quiz section.
The silicon content of quartz is 50%. Can anyone name any other gem material (aside from synthetic moissanite) that doesn't have a silicon content of LESS than quartz? :D


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PostPosted: Tue Apr 28, 2009 12:44 pm 
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In other words, a Si content greater that quartz?
:wink:


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